1. Technical Field
The invention relates to improvements in the performance of computer networks. More particularly, the invention relates to increasing performance of HTTP over long-latency links by pre-fetching objects concurrently via aggregated and flow-controlled channels.
2. Description of the Prior Art
Internet Web pages embed many types of URLs and objects. Standard browsers that display Internet Web pages can fetch some of these objects in parallel from their Web server repository. Schemes that use a browser's capability to fetch objects in parallel reduce the time taken by a browser to display pages that have many embedded objects. However, the degree of parallelism is limited due to backward compatibility, effectiveness of TCP flow control, and simplicity of browser implementation when downloading certain types of objects, such as JavaScripts and StyleSheets. The currently well-known Web browsers always download JavaScripts in sequence and StyleSheets in a separate phase.
The sequential fetching of objects degrades the end user experience with such URLs in high latency and low bandwidth networks, such as radio access networks. In short, servers are waiting for new requests to arrive but clients do not issue them until previous corresponding responses are received. This causes the link to be under used.
A general purpose cache on a browser is used to improve the time taken to revisit the same Web page. However, the general purpose cache does not help the first visit to a Web page over a wireless link. Also, a subsequent revisit may not be of benefit if the browser has cleared parts of its cache to accommodate objects from subsequent fetches from other Web sites. Thus, the use of a general purpose cache does not provide a consistent and predictable improvement in performance.
The HTTP 1.1 Request Pipelining standard (RFC 2616) allows the degree of concurrency to be increased if it is properly employed when both ends support it. However, modern browsers do not use it in an optimal fashion for many reasons, such as backward compatibility, simplicity of implementation, and effectiveness of flow control. Thus, the standard does not change the browser behavior, and therefore fails to optimize the link use at all times.
It would be advantageous to provide a method and apparatus that mitigates the negative impact of sequential access in low bandwidth and high delay networks without altering browser behaviors.